RICHARD SPENCER

An Iranian nuclear scientist claimed by Tehran to have been abducted by the US has sought refuge in Pakistan's embassy in Washington, Iranian state television said.

In a dramatic development in a long-running mystery, Shahram Amiri was said to be demanding to be allowed to return home. Mr Amiri disappeared last year while on a pilgrimage in Saudi Arabia.

Iran claimed he had been seized by the Saudi intelligence services working in collaboration with the CIA. Washington said such claims were "ridiculous" but shed no light on what happened to him.

The American television channel ABC reported it had been told by official sources that he had defected voluntarily and was providing information to the US authorities.

Intelligence websites said he had been "turned" while on trips to Frankfurt and Vienna, and had provided detailed information on the secret uranium enrichment plant the Iranians were discovered to be building.

Iran and the US have had no diplomatic relations since the Islamic revolution in 1979, and national interests are looked after by the Pakistani embassy in Washington and the Swiss embassy in Tehran respectively.

Mehr, an Iranian news agency, reported yesterday that Mr Amiri, a nuclear researcher at Tehran's Malek Ashtar University who also worked for the Iranian Atomic Energy Organisation, "went to Iran's interest section and asked for a quick return to Tehran".

Yesterday, a spokesman for Pakistan's Ministry of Foreign Affairs in Islamabad said Mr Amiri had been "dropped off" at the Iranian interests section of the Pakistani embassy in Washington at 6.30 pm local time on Monday.

"He was dropped there by someone," said Abdul Basit. "He's in the Iranian interests section, not in the Pakistan embassy per se. They are making arrangements to repatriate him."

The Iranian interests section is in a separate building, about three kilometres from the Pakistani embassy. Mr Basit said he did not know how Mr Amiri had got there or how he would be sent back to Iran.

Neither Pakistani embassy nor US State Department officials were immediately available for comment. If the report were true, it will provoke an awkward and embarrassing diplomatic stand-off for the US.

In the past two months, a series of videos have emerged which seem to be of Mr Amiri. In the first and third, shown on Iranian television, a man is seen talking into what appears to be a computer video phone, claiming he has escaped from his American captors and wants to come home. "I could be re-arrested at any time by US agents," he said in the second, released two weeks ago. He claimed to have been tortured.

There was speculation in the US that the videos were attempts to prevent retaliation against his family by the Iranian authorities.

In the second video, recorded to professional standards, the same man talks straight to camera and says he is safe and is studying in the US.

The Iranian authorities said at the end of June they were presenting evidence to the Swiss embassy that Mr Amiri had been abducted, and demanding an investigation by the US authorities.

Last month the CIA chief, Leon Panetta, said Iran had now produced enough low-enriched uranium to make two nuclear weapons within two years.